Charge forming means



July 7, 1959 A. D. MCDUFFIE 2,893,7.

CHARGE FORMING.' MEANS Filed Jan. 18, 1957 4 SheVets-Sheet i July 7,1.959 A. D. MCDUFFIE 2,893,711

v CHARGE FORMING MEANS Filed Jan. 18, 1957 4 Sheets-Sheet 2 IN VEN TOR.

AWORNEY July 7, 1959 A. p. MQDUFFH; 2,893,711

CHARGE FORMING MEANSv Filed Jan. 18, 1957 4 Sheets-Sheet 3 ATVOQNEY July7, 1959 A D MoDUFFlE 2,893,711

CHARGE F ORMING MEANS Filed Jan. 18, 1957 4 Sheets-Sheet 4 255 ffii fig#l ATTORNEY' United States Patent O 2,893,711 CHARGE FoRMiNG Archie D.McDullie, Berkley, Mich., assignor to General Motors Corporation,Detroit, Mich., a corporation of Delaware Application January 18, 1957,Serial No. 634,915 s Claims. ((31.261-23) The present invention relatesto internal combustion engines and more therefor.

In an engine of the so-called spark ignited variety, a combustiblecharge of atomizedV air and fuel is compressed and ignited in thevarious engine cylinders. In order to obtain themaximum fuel economy aswell as lmaximum'performance from such an engine,it is essential lthatthe air and fuel therein be properly mixed with each other in somepredeterminedproportions. One means of metering the fuel is to employ aventuri or similar device 'in the induction system through whichinduction air flows andproduces a vacuum signal the magnitude of whichis indicative of the mass or'quantity of air entering the engine.`Metering means responsive to the amount of `this 'vauum are thenemployedVfor metering the fuel in terms thereof. In order tol insure a positiveand accurate action of the metering means, due to hysteresis, friction,etc the vacuum transmitted tothe metering means'must be in excess ofsome minimum' amount. In order to 'obtain a vacuum in excessof theminimum amount during the periods of low air ow occurringin the idlerange, the venturi must have a small throat. Although a vacuum ofadequate magnitude c an be obtained at idle in this manner, sucha'venturi presents a serious restriction to the flow of airtherethroughduring full throttle' operation. As a` practical matter this restrictionnormally -lowers the volumetric efficiency vof the vengine and thereforematerially limitsthe maximum power-output of the engine.Accordingly,"'heretofore ithas been the' practice, particularlyinCarburetOrs, to employ a plurality o f venturis for meteringithe fuel.Normally each of these venturis have separate throttle 'valves whichareinterconnected with each e other. During light'loads only the primarythrottle valve is open. However, when -the opening'of the primarythrottle valve exceeds somepredetermined amount, the secondary throttlevalve will commence to open along with the primary throttle. Thus thepercentageof airow throughthe secondary passage will progressivelyincrease with vthe load until .bothk of 'theth'r'ottles reach the vfullyopened position at approximately the same time.` It may thus b e seenthat the proportions by which the air how divides between hthe` twoventuris will vary as the throttleA valve settings vary. In a'carburetorvof this typea separate fuel jet may be disposed in each' of theventuris and thus the fuel will beimetered -by separate means for eachventuri. As a 'result the separate metering meanswill always meter thefuelon the basis `of the air vflowing therepast and the proportions bywhich the fuel divides will not atfe'ct the air-fuel ratio. Inothervwords the use of two independent metering means will eliminate anydisruption Vor variations Aof the chargingcharacteristics asparticularly to the fuel 'supply systems the air flow gradually changesfrom ljust-one venturi to a multiplicity of venturis.

Althoughfsuch arrangements have performed satisfactorily on present daycarburetors, there are times `when the use of a compound `inletisdesirable but the use 0f a separate metering` means'for each oftheinlets is 2 impractical. For example, in one form of fuel injectionsystem a pressure differential representing the mass of air entering theengine and 'a pressure differential representingy 'the' quantityof'f'fuel beingconsumed are balanced against each other`in order to'maintain the desired airfuel'ratio'. 'The mechanisms -for-balancing thepressures are sensitive and -fa'irly expensiver As a result practicalconsiderations preclude theA use'` of two such units in one fuel systemveveii'if it' is necessary to employ a compound intake. Accordingly,Yfuel injection -gs'y`stems in general andthe mass'air ow typeparticular have employed only'a'single in'letthat is operative over Vtheentire engine operating range'. Asa result the design of the Venturi isa compromise usually resolved by making the venturi vas large aspossible while still providing the'required minimum Vacuum at idle. Thusthe operation of the engine has normally been impairedat either lightload operation and/ or heavy load operation.

It is now` proposed to provide a fuel injection system having afuelmetering mechanism and an'inductiori inlet which has arestrictionthat will develop a large pressure differential atidle orlight `load operation but will not materially impede the flow of airinto the engine at high speed'. This is tobe accomplishedby-providing aninduction intake having a'primaiyinlet and a-se'condary inlet that aredisposedfiri4 parallel with each other and joined together'so that asingle throttle valve will retain complete control over *the'volume ofair entering the engine.t Ihe-primaryinl'e't may comprise a venturihavin'gi-a throat area-sufficiently small to produce an adequate vacuumyeven 1at idle for 'operating the metering mechanism.` During lightloads, i.e., below some predetermined amount, a secondary valve in thesecondary inlet will'rem'ain' completely closed and prevent the flow ofany air therethrough. The vacuum drop in the venturi throat v`may thenbe employed to meter the fuel flow by being balanced against thefuelpressuredrop across an orifice in the fuel'line. However when the air owthrough the `engine approaches an amount where the restriction of theventuri begins to limit the air flow, the valve in the secondary inletmay open and allow air to `flow through 'both the primary andsecondary'inlets. Since the amount of airflow through `thesecondary'inlet has f no direct 'effect on the metering mechanism, itmay be free of any metering restrictions and have alarge enough crosssection to present a'minimum air iiow therethrough.

At should be noted that when the metering of the `fuel is dependent uponthe proportions between a'fu'el pressure amount of restriction to vfthe'differential across a flow restrietion such as 'an orice action `andthe charge in balance at all times; Although the transition fromtheventuri to the secondary inlet may be gradual, in order to simplifythe controls, it has been found preferable that both lthe secondaryinlet valve and the secondary metering orifice" be either `totally`inoperative or totally operative. Thus the secondary inlet v alve andorifice notonly become operativ@ simultaneously but will also move fromthe fully closed position to vthe fully open position .substantiallyvsystem embodying the present invention.

Figure 2 is a diagrammaticview of a fuel injection system embodying amodified form of the invention.

Figure 3 is a diagrammatic view of a portion of the embodiment in Figure2 with the parts being broken away and in section.

Figure 4 is a fragmentary diagrammatic view of a portion of anotherembodiment of the present invention. Referring to the drawings in moredetail, the present invention may be incorporated in a charge formingmeans adapted to be employed on any type of engine 12. however, in thepresent instance, the means 10 is particularly adapted for use on anengine 12 of the so-called spark ignited variety wherein a combustiblecharge of air and atomized fuel is formed in the induction system 14 andcompressed in the engine cylinders and then ignited by means of anelectrical discharge across a spark gap or similar element located inthe engine cyliners. The engine 12 includes a pair of 'angularlydisposed banks of .cylinders A cylinder head is secured to each bankwith intake passages 16 extending therethrough to communicate with thecombustion chambers.

This induction system 14 for the engine 12 includes an air manifold 17having an intake l18 communicating with .the atmosphere and a pluralityof branch passages 20 which are interconnected with the various intakepassages 16 for supplying the induction air to the cylinders. A

.throttle valve 22 may be provided at any suitable location such as inthe intake 18 for controlling the llow of air through the manifold 17.The intake 18 includes a primary venturi passage 24 having a restrictedthroat 26 and a secondary inlet passage 28 which is disposed in parallelto the primary venturi passage 24. The inner ends of these two passagesare interconnected with each other so as to discharge into the inductionmanifold 17 through a common passage 30. In order to control the totalamount of air flow through the induction system 14, the throttle valve22 may berdisposed inthe passage 30 downstream of the junction of thetwo passages 24 Yand 28. Although the primary venturi passage 24 remainsopen all of 4the time a secondary valve 32 may be provided in thesecondary inlet passage 28 for controlling the flow of air therethroughwithout directly affecting the air flow in the primary venturi passage24.

In order to charge the air flowing through the induction system 14 withfuel to thereby form a combustible charge, a pressurized fuel system 34is provided that positively injects the fuel into the branch passages 20immediately adjacent the intake Valves 36. In the present instance thisfuel system 34 includes a storage tank 38,

pressure boosting means 40, a metering mechanism 42 and means 44 fordistributing the fuel to the cylinders. The pressure means 4l! includesone or more fuel pumps 4S capable of delivering the fuel in sufficientquantities and pressures to actuate the system 34. The discharge line 46from the pump 45 includes a filter 48 and is connected to a pressurerelief valve 50 effective to regulate the fuel pressure by by-passingany surplus fuel for return to the storage tank 38.

In order to meter the fuel in proportion to the air flow,

the fuel metering mechanism 42 includes a fuel metering v valve 52therein. The upstream side of this valve 52 is interconnected with thepressure relief valve 50 by a fuel line 54 and' the downstream side ofthe valve 52 is interconnected with the fuel distributor 44 by means ofa.

` metered fuel line 56 having a pair of parallel branches 58 and 60 eachof which Vhas a metering restriction 62 -and 64 therein.l Although theserestrictions 62 and 64 insure the proper operation of the engine. Inother words may be of any suitable type, they are preferably orificesthat create a pressure differential thereacross similar to` the pressuredifferential in aventuri. The primary braucht 58 is preferably open atall times whereas the secondary' branch 60 includes a secondary fuelvalve 66.

Although the distributor 44 may be any suitable flow-- divider, in thepresent instance it includes a rotor 68 driven. by the engine camshaftfor delivering the fuel to the noz-- zles 70 in timed relation with theopening of the intake:

valves 36.

The metering mechanism 42 includes a housing having: an air diaphragm 72and a fuel diaphragm 74 therein: which are operatively interconnectedwith each otherand with the metering valve 52 by a reciprocable shaft76. The air diaphragm 72 has one side 78 thereof exposed to atmosphericair pressure while the opposite side forms a movable wall of a vacuumchamber interconnected with the venturi throat 26 by a vacuum or controlsignal line.-82. Thus there will be a pressure differential across theair diaphragm 72 that will create a force on the shaft 76 indicative ofthe volume of air entering the engine and .tending to open the meteringvalve.

The fuel diaphragm 74 separates' a pair of fuel chambers 84 and 86. Thehigh pressure chamber 84 is connected tothe metered fuel line 56anterior to the metering restrictions 62 and 64 by a tube 88 while thelow pressure chamber -86 on the opposite side of the diaphragm 74 isconnected to the' fuel line 5 6 posterior to the metering restrictions62 and 64 by another tube 90. Since the hydraulic resistances of therestrictions 62 and 64 will create a pressure differential thereacrossproportional to the fuel flow, thediaphragm 74 will create a secondforce on theshaft 76 proportional to the fuel flow and tending to closethe valve 52 in opposition to the rst force. It may thus bevseen that asthe air flows through the venturi 24 it will create a vacuum in thethroat 26 of the venturi. This vacuum will produce a force on thediaphragm 72 that will tend to move the shaft 7 6 to the right (Figurel) and open theA metering valve 52, thereby increasing the fuel flow. Atthe same time the fuel distributed to the cylinders, i.e., the meteredfuel, will flow through the metering orifices `62 and/0r 64 and producea pressure diiferentialthereacross that will tend to move the valve 52to the left and close the valve 52 to thereby decrease the .fuel flow.It will lthus be seen that the fuel ow and air flow will produce opposedpressure forcesbnjthe dia- .phragms 72 and 74 that will move the shaft76 axially and adjust the valve 52 until the forces are balanced.

When a stable condition is thus established the air and fuel flows arein some predetermined proportions.

When the engine is idling or driving a light load the -A secondary valve32 in the secondary passage 28 is prefthe primary venturi 24 may have asufficiently small throat 26 to develop an adequate vacuum even at lightloads to overcome any friction, etc., and positively operate thediaphragms, fuel metering valve, etc. If the size of the meteringrestriction 62 is properly chosen the air and the fuel pressuredifferentials will actuate the fuel valve 52 to maintain the air-fuelratio at the desired amount to the primary metering orifice 62 ismatched with the small venturi 24.

Since the venturiy throat 26 is sufficiently restricted to produce alarge vacuum at the limited air liow occurring during engine idling andlight loads, at heavier loads with Athe increased air ilow the venturi24 will present a large L resistance .tothe induction-air ow and as aresult will A decrease the volumetric efficiency of the induction system7a: r4. accordingly. the Secondaryjnletlimey lis PfQYiFd in parallel tothe primary inlet 24 so as to supply additional air during heavy loads.It has been found preferable for the's'econdary inlet to comprise acylindrical passage 'free' from any ow restricting obstructions therein.

The secondary throttle valve 32 in the secondary passage 28 controls theair ow therethrough and is actua-ted by a trigger unit 92`that willretain the valve 32 closed when necessary to insure a large enough airflow through -the venturi 24 to always create aY strong vsignal and willopen the valve 32 when necessary to prevent a decrease in the volumetriceiciency of fthe'engine. Although the trigger unit 92 may be responsiveto any suitable type of signal Since the volume of air owing throughlthe Vinduc- {tion'sys'tem 14 is the primary consideration, thetriggering signal is preferably indicative of such a flow. Accordingly,in the present instance the trigger unit 92 includes a spring biaseddiaphragm 94 that has one side exposed to atmosphere and the other `sideexposed to the VKyacuum ina chamber96 .connected to the intake manifoldposterior to the throttle valve 22. The diaphragm 94 is connected to abooster vacuum valve 9S by a lost motion linkage 100 that will allow thevalve to remain closed unless the intake vacuumV is less than somepredetermined amount. The booster valve 98 isconnected to-the'diajphragm 102 inthe secondary fuel valve 6.6 by a line 103 vandtothe chamber 104 for the diaphragm 105 in the control'for the secondarythrottle valve 32 by a line 106 having' arestric'tion 108 therein. Itmay thus be seen that -Wherever the induction vacuum is less than somepredetermined amount the diaphragm 94 Will open the valve permittingbooster vacuum in a conduit 109 to act in lline 103 to open thesecondary throttle valve 32 and the secondary fuel valve 66. The lostmotion linkage 100 permits the diaphragm 94 to move considerably beforeyit 4opens'or closes thevalve 98. The vacuum required to close the valve93 is considerably below that required to :open the valve 98 to therebyprevent hunting in the zsystem.

The operation of this system may be summarized as :follows:

' When the engine is lightly loaded and the air flow is small, the'throttle valve 22 is closed or nearly closed and there will be a'highvacuum in the intake manifold. This high vacuum will be transmitted tothe chamber 196 by the line 110 and will cause the diaphragm 94 tocompress the spring 112. Under these circumstances there will besufficient slack in the lost motion linkage 100 to allow booster vacuumvalve 98 to remain closed. Thus the springs 114 and 116 lwill bias thesecondary inlet valve '32"and the secondary fuel valve 66 closed'.`Conse- -quently, all of the air and fuel will ow through the primaryventuri 24 and the primary orifice 62 respectively. 4If the primary fuelorifice 62 is matched to the primary venturil 24 the motion of the fuelmetering valve tobalance the forces on the air and fuel diaphragms 72land 74 'will insure the air and fuel ow inv thedesired proportions`.`As the throttle valve 22 opens the intake vacuum ydecreases until all ofthe slack disappears from the lo'st `rnotion 'linkage 1700 and thebooster vacuum valve 98 opens. As soon as this occurs the source ofbooster vacuum will be interconnected with the secondary'throttle`diaphragm chamber and the diaphragm chamber inthe 'secondary fuel valve66. This will substantially instantly open the secondary fuel valve 66and allow the fuel to How through both the primary and secondary fuelrnetering ,orifices 6 2 vand 64. Simultaneously therewith, the air tinVthe secondary inlet actuator will be exhausted therefrom and cause thesecondary inlet valve 32 to open. It 'may ybe seen that if the combinedresistances of the two .orifices 62 and 64 are matched tothe divided airflow through the primary venturi 26 and the secondary Vinlet 2S' ,thediaphragme 72 and 74 and metering valve 52`wil1 'insure thedesiredair-fuel ratio as before.

Thus; yilow of induction air Will be relatively unrestrictedlas` the airmay'divide itsflow and enter through Aboth' 'the secondary inlet 28a`ndthe primary venturi 24.

If the `secondary throttle valve :3 2 gradually opens with increasingairflow, itis necessary to increase the fuel ow through the secondaryorifice in the identical manner in order to maintain vthe desiredairfuel ratio. In .other words the ratio o f lthe division of the vairow through primary venturi and secondary inlet and the division of fuelflow through the primary and secondary metering orifices must besimilar. kHowevenit has been found that byin- Vst antaneously completely.opening the second inlet valve and the transfervalve, there will be noblending problems which might otherwise occur vin gradually openingthese two valves.

It maybe found desirable to place the restriction 108 in the vacuum lineto the diaphragmchamber 104'to 'slightly retard the flow of airtherefrom. This will cause a slight time delay inthe opening of thesecondary throttle valve 32, thus insuring the secondary fuel valve 6 6opening slightly `ahead of the secondary throttle valve 32. -As a resultthere may 'be short'intervals Aduring which lthe charge is excessivelyrich, a condition desirable during acceleration, but more important itwill also .eliminate Iany `lean condition that' might .cause'a misfiring.of the engine.

lBy maintaining the valves 32 and 66 either completely opened orcompletely closed, the .air will either flow entirely through theprimary venturi v24 or divide its flow between the venturi `24 andsecondary inlet 28 in some predetermined ratio. Thus if the' primaryorifice .62 is matched -to the primary venturi 2.4 and the primary .and

secondary orifices A62 and 64 are matched to the primary be maintainedconstant at all times. 1

As an alternative, the .embodiment of the charge forming means 120'disclosed in Figures 2 and 3 may .be ernployed. This embodimentincludes an induction system 122 having an intake manifold 124withaninlet riser 126 in the center thereof and a plurality of branchpassages 128 arranged to communicate with the cylinders in a V-typeengine. An intake assembly 130 may be mounted on the riser 126 fordrawing the induction air from the atmosphere and Supplying it to themanifold 12.4. The present intake 13 0 includes a primary venturipassage'132 having Aa restricted throat 134 and a secondary inletpassage 136 in parallel thereto. The secondary inlet passage 136includes a throttle valve 13.8 normally biasedclosed by a spring 140 butadapted to be opened by the vacuum in a chamber 142 behind lthediaphragm 144. A pair of throttle valves 146 may be provided on a commonshaft 148 passing through the lower Vends of the primary and secondarypassages 132 and 13.6 -for 'controlling 4the How of induction air intoythe engine while a choke valve '150 is disposed upstream thereof fortemporarily increasing the vacuum inthe throat 134 ofthe venturi Y13:2.V

In order vto form a' combustible charge Aof air and fuel, a fuelinjection system 152 is provided which includes'a fuel storage tank 154,fuel pumping means 156, Aa pressure relief valve 15S, a meteringmechanism 16.0 and'a distributing mechanism 162 which will distributethe'fuel to various nozzles 164 located in the various cylindersporbranch passages of the manifold 124. The vpumping means 156 may includea' single fuel pumpor as'inithe present embodiment it includesa'transfer pump 165 and `a booster pump 166.

The pressure relief valve 153 is of the by-pass type and includes a.diaphgram 168-responsive to the-fuel pressure and a spring 17.0 biasingthe valve closed. The ,ten-

lsionof .the spring 170 maybe a fixed ,amount or if `desired 'diaphragms186 and 188 oppose each other.

in position. .The air diaphragm 186 forms an inner chamor high pressurefuel chamber 196 and an outer or low pressure fuel chamber 198. Thesetwo chambers 196 'and 198 are interconnected with each other by a pairof primary metering orifices 200 and 202 so that the fuel flowingtherebetween will create a pressure differential across the fueldiaphragm 188. A yoke 204 pivoted at the pin 206 in the upper portion ofthe center wall 208 has one arm 210 attached to the center of the airdiaphragm 186 and the other arm 212 attached to the center of the fueldiaphragm 188 so that the forces on the two A fuel metering valve 214 inthe inlet 176 includes a plunger 216 `that engages the lower end 218 ofthe other arm 212 to be actuated thereby. It may thus be seen that theforces on the two diaphragms 186 and 188 will be effective to move theyoke 204 and actuate the metering valve 214.

The outlet of the low pressure chamber 198 is Connected to a meteredfuel line 220 that is connected to a pressure check valve 222 formaintaining the pressure in the system anterior thereto, in excess ofsome predetermined vamount and to the fuel distributor 162.

In addition to the primary metering orifices 200 and 202, a secondarymetering orice 224 and an enrichment orifice 226 are provided inparallel thereto. Thus any fuel ow through these orifices will also beeective to contribute to the pressure differential across the diaphragms186 and 188. The rich orifice 226 is controlled by a valve 228 actuatedin response to the intake vacuum.

During the normal operating range the valve 228 will be closed but whenthe induction vacuum is low, as occurs during full throttle operation,the valve 228 Will open and as a result the charge will be enriched toprovide maximum power.

The secondary orifice 224 is controlled by a valve 230 normally retainedclosed by a spring 232 and opened by a diaphragm 234 responsive to thepressure in the chamber 236 therebehind. The pressures in the diaphragmchambers 142 and 236 are controlled by a booster vacuum valve 238 in atrigger unit 240. The valve includes a ball 242 that is positioned by anover center snap spring 244 to block either the vent 246 or the boostervacuum line 247. The spring 244 is engaged by an arm 248 on thevthrottle shaft and when the throttle valves 138 are closed or in thelight load range, the spring 244 will retain the booster valve 238closed as shown. At some point during the opening of the throttle, thearm 248 will cause -the spring 244 to pass over center and open thebooster valve 238. When this occurs the booster vacuum will appear inboth the secondary fuel valve diaphragm chamvber 236 and the secondarythrottle diaphragm chamber 142. As a result the secondary metering orice224 and -the secondary inlet 176 will completely open substan- .Y tiallysimultaneously.

The operation of this embodiment may be summarized as follows:

During idle and part throttle operation the arm 248 on the throttleshaft Will deflect the spring 244 so as to close the booster vacuumvalve 238. -Thus the springs 140 and 232 acting on the diaphragms 144and 234 will insure the valves 138 and 230 being retained in the closedpositions. primary orifices 200 and 202 and all of the air flows As aresult all of the fuel flows through the through the primary venturi132. These forces tend to swing the yoke 204 for opening or closing thefuel metering valve 214 and regulating the fuel ow. Since the fuelforces and air forces are iny opposition to each other and they willposition the fuel valve 214 to cause the two pressure differentials andtherefore the air and fuel flows l to be maintained ink somepredetermined proportions. If the resistances of the venturi 132 and theprimary orifices 200 and 202 'are properly matched, the resultantchargel ployed.

secondary fuel metering orifices 200, 202 and 224. At

the same time the diaphragm 144 will open the secondary throttle valve138 and thus allow air to enter through both the venturi 132 and thesecondary inlet passage 136. If the primary and secondary fuel orificesare matched against the divided air flow, the desired air-fuel ratiowill be maintained. This ratio is normally suitable for maximum economy;however, if the intake vacuum drops sufliciently the power enrichmentorifice 226 will open for a rich charge suitable for maximum power. Whenthe throttle valve 146 closes the spring 244 will again pass over centerand close the booster vacuum valve 238. This will open the vent 246 andallow the springs 140 and 232 to move the valves 138 and 230 and closethe secondary inlet 136 and the secondary fuel orice 224.

As a further modification, the embodiment of the charge forming meansdisclosed in Figure 4 may be em- In this embodiment the induction systemis similar to that in the previous embodiments. The intake assembly 250includes a housing 252 having a primary venturi passage 254 and asecondary inlet passage 256. The lower ends of these passages 254 and256 are joined together so as to discharge into a common passage 270vhaving a single throttle valve 272 disposed therein for controlling theamount of air flowing through the engine. The secondary passage 256 issubstantially cylindrical and free from any flow restricting meanstherein except for a secondary throttle 260. This valve 260 is normallyretained closed by a spring member 262 but a diaphragm 264 responsive tothe vacuum in the chamber 266 therebehind is effective to open the Valve260.

In order to form a combustible charge of air and fuel, a fuel injectionsystem is provided for injecting metered fuel into the charge. Thissystem may be substantially the same as that in the foregoingembodiments wherein a fuel metering valve is actuated by an airdiaphragm responsive to the vacuum in the throat 268 of the venturi 254and a fuel diaphragm is responsive to the pressure drop across a primarymetering orifice 271 and a secondary metering orifice 273. The flow offuel through the secondary orifice 273 is controlled by a valve 274biased closed by a spring 276 and opened by a diaphragm 278 responsiveto the pressure in the chamber 280.

In order to actuate the diaphragms 264 and 278 controlling the secondarythrottle valve 260 and the secondary orifice 273, a trigger unit 282 isprovided. This unit 282 includes a booster vacuum valve 284 controlledby a diaphragm 286 having the chamber 288 therebehind interconnectedwith the throat 268 of the venturi 254. The valve 284 is normally biasedclosed by a spring 290 and thus blocks the booster vacuum line 292 andopens the vent 294 to atmosphere. This will cause the the venturi 254 isadequate to produce a strong vacuum,

the diaphragm 286 will open the booster valve 284 and close the vent294. This will cause booster vacuum to appear in the diaphragm chambers266 and 280, thereby causing the diaphragms to open the secondarythrottle valve 260 and the secondary fuel valve 274. When the g air flowagain decreases, the booster valve 284 will close and open the vent 294so that the secondary throttle 260 and fuel valve 274 will also close.It may thus be seen that the actuation of the secondary throttle valve260 will be regulated directly in proportion to the quantity of air`flowing through the primary venturi 254. Consequently,

there will always be a vacuum signal of at least somepredeterminedamount irrespective of the position of the primary throttlervalye272orzthe amount'qf intake manifold vacuum.

' It isto he understood that, although the invention has been describedwith specific reference to particular embodimentsthereo it is not to hesolimited since changes and alterations therein mayy he made which arewithin the full intended scope of this invention as defined by theappended claims.

I claim:

l. Charge forming means for an engine having an induction system with anintake comprising a first inlet having means for produci-ng a signalindicative of the quantity of air flowing therethrough, a second inletin parallel with said first inlet and being free of any metering meanstherein, a secondary valve disposed in said secondary inlet to controlthe flow of air therethrough, a throttle valve disposed downstream ofsaid inlets for simultaneously controlling the total amount of air flowthrough said inlets, fuel supply means responsive to said signal andeffective to atomize metered fuel into said charge in proportion to saidcharge, means responsive to the vacuum in said induction systemposterior to said throttle valve for simultaneously opening saidsecondary valve when said vacuum is less than some predetermined amountand to modify the responsiveness of said fuel means in proportionthereto.

2. Charge forming means for an engine comprising an induction systemhaving an intake and a fuel system for injecting metered quantities ofatomized fuel into the air in said induction system, said intakeincluding a pair of parallel air inlets one of which includes means toproduce a signal indicative of the quantity of air flow therethrough andthe other of which is free of any signal producing means but includes asecondary valve therein, said fuel system including primary andsecondary fuel orifices adapted to produce a signal indicative of thequantity of fuel flow, means for maintaining said signals in somepredetermined proportions and means for simultaneously controlling theposition of said secondary valve and the operation of said secondaryorifice to maintain said air-fuel ratio in some predeterminedproportion.

3. Charge forming means for an engine comprising an induction systemhaving an intake and a fuel supply system for injecting meteredquantities of atomized fuel into the air in said induction system, saidintake including a pair of parallel air inlets, only one of whichincludes means to produce a signal indicative of the quantity of airiiow therethrough and the other of which is free of any signal producingmeans but includes a secondary valve therein, throttle means downstreamof said inlets for controlling the fiow of air therethrough, said fuelsystem including primary and secondary fuel orifices adapted to producea signal indicative of the quantity of fuel ow, metering means formaintaining said air and fuel signals in some predetermined proportionsand means responsive to the load on said engine for simultaneouslycontrolling the position of said secondary valve and the operation ofsaid secondary orifice.

4. Charge forming means for an engine comprising an induction systemhaving an intake and a fuel supply system for injecting meteredquantities of atomized fuel into the air in said induction system, saidintake including a pair of parallel air inlets, only o-ne of whichincludes means to produce a signal indicative of the quantity of airfiow therethrough and the other of which iS free of any signal producingmeans but includes a secondary valve therein, throttle means downstreamof said inlets for controlling the fiow of air therethrough, said fuelsystem including primary and secondary fuel orifices adapted to producea signal indicative of the quantity of fuel fiow, means for maintainingsaid air and fuel signals in some predetermined proportions and meansresponsive to the position of said throttle valves for retaining said 10secondary valve and said secondary orifice closed when said throttlevalve is closed more than ,some predetermined amount and effective tocompletely open said secondary valve and said secondary orifice whensaid throttle valve is open more than some predetermined amount.

`5'. .Charge formi-ng means for an enginecomprising an induction systemhaving an intake and a Vfuel supply system for injecting meteredquantities of atomized fuel into the air in said induction system, saidintake includi-ng a pair of parallel air inlets, only one of whichincludes means to produce an air signal indicative of the quantity ofair flow therethrough and the other of which is free of any signalproducing means but includes a secondary valve therein, throttle meansdownstream of Said inlets for controlling the flow of air therethrough,said fuel system including primary and secondary fuel orifices adaptedto produce fuel signal indicative of the quantity of fuel filow, meansfor maintaining said air and fuel signals in some predeterminedproportions and means responsive to the strength of said air signal forretaining said secondary valve and said secondary orifice closed whensaid signal is less than some predetermined amount and forsimultaneously completely opening said secondary valve and saidsecondary orifice when said signal is in excess of some predeterminedamount.

6. Charge for-ming means for an engine comprising an induction systemhaving an intake and a fuel supply system for injecting meteredquantities of atomized fuel into the air in said induction system, saidintake including a pair of parallel air inlets, only one of whichincludes means to produce a signal indicative of the quantity lof airflow therethrough and the other of which is free of any signal producingmeans but includes a secondary valve therein, throttle means downstreamof said inlets for controlling the ow of air therethrough, said fuelsystem including primary and secondary fuel orifices adapted to producea signal indicative of the quantity of fuel fiow, means for maintainingsaid air and fuel signals in some predetermined proportions and meansresponsive to the amount of vacuum downstream of said throttle valvesfor retaining said secondary valve and secondary orifice completelyclosed when said vacuum is in excess of said predetermined amount andfor completely opening said secondary valve and said secondary orificewhen said vacuum is less than some predetermined amount.

7. Charge forming means for an engine comprising an induction systemhaving an intake and a fuel supply system for injecting meteredquantities of atomized fuel into the air in said induction system, saidintake includ'- ing a pair of parallel air inlets, only one of whichincludes means to produce a signal indicative of the quantity of airfio'w therethrough and the other of which is free of any signalproducing means but includes a secondary valve therein, throttle meansdownstream of said inlets for controlling the flow of air therethrough,said fuel system including primary and secondary fuel orifices adaptedto produce Ia signal indicative of the quantity of fuel flow, means formaintaining said air and fuel signals in some predetermined proportions,and means responsive to an operating condition of said engine forretaining said secondary valve and said secondary orifice closed andeffective to completely open said secondary valve and said secondaryorifice whenever said engine operating condition is exceeded.

8. An induction intake for an engine having an induction system and afuel supply system for atomizing metered quantities of fuel into the airin said induction system, said induction intake comprising a pair ofinlets disposed in parallel with each other, throttle means disposeddownstream of said inlets for controlling the flow` through said inlets,one of said inlets including means for producing a signal indicative ofthe flow therethrough and effective to actuate said fuel supply systemfor controlling a quantity of metered fuel atomized in said` charge, theother of said inlets including a secondary valve for controlling theamount of air ow through said other inlet, means responsive to apredetermined engine operating condition for retaining said secondaryvalve closed and for completely opening said secondary valve wheneversaid predetermined engine operating condition is exceeded.

References Cited in the file of this patentv UNITED STATES PATENTSStrebinger Nov. 2, 1948 Stresen-Reuter Oct. 10, 1950 l Mock Jan. 27,1953 Ronalet et al Aug. 6, 1957

